Mechanical seal with sensor

ABSTRACT

A system and method for monitoring a dry gas seal positionable between a stationary housing and a rotatable shaft. A plurality of sense elements may rotate in response to the rotation of the rotatable shaft and a speed sensor may sense the speed of the rotatable shaft at speeds below one thousand rotations per minute based on sensing the plurality of sense elements. A processor may receive output signals from the speed sensor and may establish a position of the dry gas seal or an operating condition of the dry gas seal based on the signal from the speed sensor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 62/790,969, filed Jan. 10, 2019, and U.S. Provisional ApplicationSer. No. 62/742,707, filed Oct. 8, 2018 which are incorporated herein byreference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to mechanical seals. Moreparticularly, this disclosure relates to mechanical seals that includesensor and/or monitoring systems configured to monitor seal operatingconditions.

BACKGROUND

Seals, such as dry gas seals, are used in a wide variety of applicationsincluding, for example, gas compressors and other rotating equipmentsuch as gas and steam turbines, turbo expanders, centrifugal pumps, andthe like. Such seals are used to seal a rotating interface between ashaft and a housing of a compressor and/or other rotating equipment. Theprinciple of dry gas seal technology is that the sealing faces arenon-contacting and a clean and dry gas is allowed to pass through theseal interface. During operation, a portion of the flow of the gas beingprocessed may be diverted from the operating flow and filtered to removeparticulate and liquid mist that may be present in the operating flow.This diverted gas flow may be further processed, for example,superheated to a temperature above its dew point, and provided to thedry gas seal as an operating fluid.

SUMMARY

The present disclosure relates generally to dry gas seals, and moreparticularly, devices, systems, and methods for establishing andmonitoring lift off and touch down speeds of a dry gas seal to providean assessment of seal operating conditions and/or degradation of dry gasseal faces.

In one example, a seal monitoring system for a dry gas seal assembly isdisclosed. The seal monitoring system may include a dry gas seal, anacoustic emissions sensor, a speed sensor, and a processor. The dry gasseal may have a stator portion with a first seal face and a rotorportion with a second seal face, wherein the dry gas seal may bepositioned between a stationary housing and a rotatable shaft, and therotor portion may be configured to rotate with the rotatable shaft. Theacoustic emissions sensor may be configured to sense when the first sealface and the second seal face are in an operational condition relativeto one another and output a signal indicative of the operationalcondition. The speed sensor may sense the speed of the rotatable shaftat speeds below one thousand (1,000) rotations per minute (RPMs) and maybe configured to output a signal indicative of a rotational speed of therotatable shaft. The processor may be configured to receive the signalfrom the speed sensor and the signal from the acoustic emissions sensor,and may establish an operating condition of the dry gas seal based onthe signal from the speed sensor when the first seal face and the secondseal face reach the operational condition relative to one another.

Alternatively or additionally to any of the embodiments above, theoperational condition of the first seal face relative to the second sealface may be a lift-off operational condition of the dry gas seal.

Alternatively or additionally to any of the embodiments above, theoperational condition of the first seal face relative to the second sealface may be a touch-down operational condition of the dry gas seal.

Alternatively or additionally to any of the embodiments above, theoperational condition of the first seal face relative to the second sealface may include a lift-off operational condition of the dry gas sealand a touch-down operational condition of the dry gas seal.

Alternatively or additionally to any of the embodiments above, theprocessor may be configured to establish the operating condition of thedry gas seal based on the signal received from the speed sensor when thedry gas seal reaches the lift-off operational condition and the signalreceived from the speed sensor when the dry gas seal reaches thetouch-down operational condition.

Alternatively or additionally to any of the embodiments above, the speedsensor may be a Hall-effect sensor.

Alternatively or additionally to any of the embodiments above, the speedsensor may sense speeds of the rotatable shaft at speeds below fivehundred (500) rotations per minute (RPMs).

Alternatively or additionally to any of the embodiments above, the speedsensor may be configured to sense speeds of the rotatable shaft atspeeds below one thousand (1,000) RPMs based on sensing two or moresense elements configured to rotate with the rotatable shaft.

Alternatively or additionally to any of the embodiments above, the twoor more sense elements may include slots disposed on the rotor portionof the dry gas seal.

Alternatively or additionally to any of the embodiments above, the sealmonitoring system may further comprise a ring configured to rotate withthe rotatable shaft, wherein the ring includes the two or more senseelements.

Alternatively or additionally to any of the embodiments above, one ormore of the two or more sense elements may include an indicator elementconfigured to allow the processor to determine a rotational direction ofthe rotatable shaft based on the signal output from the speed sensor.

Alternatively or additionally to any of the embodiments above, theprocessor may be configured to determine an axial position of the rotorportion relative to the stator portion based on the signal output fromthe speed sensor.

In another example, a method of operating a dry gas seal monitoringsystem having a dry gas seal forming a seal between a housing and arotatable shaft is provided. The illustrative method may includedetermining when one of a separation of a first seal face from a secondseal face of the dry gas seal and a contact of the first seal face withthe second seal face occurs. The illustrative method may furtherinclude, determining a rotational speed indicative of a speed of therotatable shaft, associating the rotational speed with an occurrence ofone of the separation of the first seal face from the second seal faceand the contact of the first seal face with the second seal face, anddetermining an operating condition of the dry gas seal based on theassociation of the rotational speed with an occurrence of one of theseparation of the first seal face from the second seal face and thecontact of the first seal face with the second seal face.

Alternatively or additionally to any of the embodiments above,determining an operating condition of the dry gas seal may includemonitoring, over time, rotational speeds associated with occurrences ofone of the separation of the first seal face from the second seal faceand the contact of the first seal face with the second seal face.

Alternatively or additionally to any of the embodiments above, themethod may further comprise establishing a first baseline speed for theseparation of the first seal face from the second seal face duringrun-up and establishing a second baseline speed for the contact of thefirst seal face with the second seal face during run-down; and whereinmonitoring, over time, the rotational speeds associated with occurrencesof one of the separation of the first seal face from the second sealface and the contact of the first seal face with the second seal facemay include one of comparing the first baseline speed with therotational speeds associated with subsequent occurrences of theseparation of the first seal face from the second seal face andcomparing the second baseline speed with the rotational speedsassociated with subsequent occurrences of the contact of the first sealface with the second seal face.

Alternatively or additionally to any of the embodiments above,determining an operating condition of the dry gas seal may includemonitoring, over time, the rotational speeds associated with occurrencesof both of the separation of the first seal face from the second sealface and the contact of the first seal face with the second seal face.

Alternatively or additionally to any of the embodiments above, themethod may further comprise establishing a first baseline speed for theseparation of the first seal face from the second seal face andestablishing a second baseline speed for the contact of the first sealface with the second seal face; and wherein determining an operatingcondition of the dry gas seal may include one of comparing the firstbaseline speed with rotational speeds associated with occurrences of theseparation of the first seal face from the second seal face andcomparing the second baseline speed with the rotational speedsassociated with occurrences of the contact of the first seal face withthe second seal face.

Alternatively or additionally to any of the embodiments above,determining an operating condition of the dry gas seal may be based onthe association of rotational speeds with occurrences of both of theseparation of the first seal face from the second seal face and thecontact of the first seal face with the second seal face.

Alternatively or additionally to any of the embodiments above,determining an operating condition of the dry gas seal may include oneof comparing rotational speeds associated with occurrences of theseparation of the first seal face from the second seal face to alift-off speed threshold and comparing rotational speeds associated withoccurrences of the contact of the first seal face with the second sealface to a touch-down threshold.

Alternatively or additionally to any of the embodiments above,determining when one of the separation of the first seal face from thesecond seal face and the contact of the first seal face with the secondseal face occurs may be based on a signal from an acoustic emissionssensor of the dry gas seal system.

In another example, a dry gas seal is disclosed. The dry gas seal mayinclude a rotor portion, a stator portion, a plurality of senseelements, and a speed sensor. The stator portion may have a first sealface and the rotor portion may have a second seal face, where the firstseal face and the second seal face may be positioned between a rotatableshaft and a stationary housing to form a seal. The plurality of senseelements may be configured to rotate in response to the rotation of therotatable shaft. The speed sensor may be at least partially securedrelative to the stator portion and may be configured to sense theplurality of sense elements. The speed sensor may be further configuredto sense a rotational speed of the rotatable shaft at speeds below onethousand (1,000) rotations per minute (RPMs) based on sensing theplurality of sense elements.

Alternatively or additionally to any of the embodiments above, theplurality of sense elements may include a plurality of slots.

Alternatively or additionally to any of the embodiments above, one ormore of the plurality of slots may include a notch configured to besensed by the speed sensor to indicate a direction of rotation of therotatable shaft.

Alternatively or additionally to any of the embodiments above, one ormore of the plurality of slots may include an axially extending taper.

Alternatively or additionally to any of the embodiments above, theaxially extending taper may taper at fifty-five (55) degrees relative toa plane perpendicular to an axis of rotation of the rotatable shaft.

Alternatively or additionally to any of the embodiments above, theplurality of sense elements may be disposed on the rotor portion.

Alternatively or additionally to any of the embodiments above, the drygas seal may further comprise a collar coupled to the rotatable shaftand configured to rotate with the rotatable shaft; and wherein theplurality of sense elements may be disposed on the collar.

Alternatively or additionally to any of the embodiments above, the speedsensor may be a Hall-effect sensor.

Alternatively or additionally to any of the embodiments above, the drygas seal may further comprise a processor configured to receive anoutput from the speed sensor; and wherein the processor is configured touse the output from the speed sensor to determine an axial position ofthe rotor portion relative to the stator portion.

Alternatively or additionally to any of the embodiments above, the drygas seal may further comprise an acoustic emissions sensor at leastpartially secured relative to the stator portion; and wherein theacoustic emissions sensor may be configured to sense a sound indicativeof an operational condition of the first seal face relative to thesecond seal face.

In another example, a dry gas seal monitoring system is disclosed. Thedry gas seal monitoring system may include a dry gas seal, a collar, aplurality of sense elements, a speed sensor, an acoustic emissionssensor, and a processor. The dry gas seal may have a first seal face anda second seal face, wherein the dry gas seal is positionable to form aseal between a stationary housing and a rotatable shaft. The collar maybe configured to rotate with the rotatable shaft and the plurality ofsense elements may be disposed on the collar. The speed sensor may beconfigured to sense the plurality of sense elements disposed on thecollar as the plurality of sense elements rotate in response to rotationof the rotatable shaft. The acoustic emissions sensor may be configuredto monitor an operational condition of the first seal face relative tothe second seal face. The processor may be configured to receive a firstsignal from the speed sensor and a second signal from the acousticemissions sensor and establish a baseline speed for the operationalcondition based on the first signal and the second signal.

Alternatively or additionally to any of the embodiments above, theprocessor may be configured to monitor changes over time in a speedsensed by the speed sensor by comparing the first signal at occurrencesof the second signal to the baseline speed.

Alternatively or additionally to any of the embodiments above, thesecond signal from the acoustic emissions sensor may be indicative ofone of a separation of the first seal face from the second seal face anda contact of the first seal face with the second seal face.Alternatively or additionally to any of the embodiments above, the speedsensor may be configured to sense the plurality of sense elements andsense speeds of the rotatable shaft at speeds below one thousand (1,000)RPMs based on sensing the plurality of sense elements.

Alternatively or additionally to any of the embodiments above, the speedsensor may be configured to sense the plurality of sense elements andsense speeds of the rotatable shaft at speeds below five hundred (500)RPMs based on sensing the plurality of sense elements.

Alternatively or additionally to any of the embodiments above, theprocessor may be configured to determine the direction of rotation ofthe rotatable shaft based on the first signal received from the speedsensor.

Alternatively or additionally to any of the embodiments above, theprocessor may be configured to determine an axial position of therotatable shaft relative to the stationary housing based on the firstsignal received from the speed sensor.

In another example, a seal monitoring system for a dry gas seal assemblyis disclosed. The seal monitoring system may include a dry gas sealhaving a stator portion with a first seal face and a rotor portion witha second seal face, the dry gas seal is configured to be positionedbetween a stationary housing and a rotatable shaft with the rotorportion configured to rotate with the rotatable shaft, a sense elementconfigured to rotate with the rotatable shaft, a sensor sensing thesense element as the sense element rotates with the rotatable shaft, thesensor configured to output a signal based on the sensing of the senseelement, a processor configured to receive the signal from the sensor,and the processor may be configured to determine an axial position ofthe rotor portion relative to the stator portion based on the signaloutput from the sensor.

Alternatively or additionally to any of the embodiments above, theprocessor may be configured to determine the axial position of the rotorportion relative to the stator portion based on an amplitude of thesignal output from the sensor.

Alternatively or additionally to any of the embodiments above, thesignal output from the sensor may include one or more pulses and theprocessor is configured to determine the axial position of the rotorportion relative to the stator portion based on the one or more pulsesin the signal output from the sensor.

Alternatively or additionally to any of the embodiments above, the sealmonitoring system may include two or more sense elements, the two ormore sense elements include the sense element, and the processor may beconfigured to determine the axial position of the rotor portion relativeto the stator portion based on one or more of an amplitude of the one ormore pulses in the signal, a pulse width of the one or more pulses inthe signal, and a width between consecutive pulses in the signal.

Alternatively or additionally to any of the embodiments above, the sealmonitoring system may include two or more sense elements, the two ormore sense elements include the sense element, and the two or more senseelements may be configured to be radially spaced circumferentiallyaround the rotatable shaft.

Alternatively or additionally to any of the embodiments above, the twoor more sense elements may be equally radially spaced circumferentiallyaround the rotatable shaft.

Alternatively or additionally to any of the embodiments above, one ormore of the two or more sense elements may be configured to be axiallyspaced from at least one other sense element of the two or more senseelements.

Alternatively or additionally to any of the embodiments above, the senseelement may have a cross-sectional shape that changes along an axiallength of the sense element.

Alternatively or additionally to any of the embodiments above, thecross-sectional shape that changes along the axial length of the senseelement may be a circular shape.

Alternatively or additionally to any of the embodiments above, thecross-sectional shape that changes along the axial length of the senseelement may be a trapezoidal shape.

Alternatively or additionally to any of the embodiments above, the senseelement may have a surface with a depth relative to the sensor thatchanges over an axial length of the sense element.

Alternatively or additionally to any of the embodiments above, the depthrelative to the sensor that changes over an axial length of the senseelement may be an axial taper in the surface.

Alternatively or additionally to any of the embodiments above, the senseelement may be disposed on the rotor portion.

Alternatively or additionally to any of the embodiments above, the senseelement may be disposed on a sleeve of the rotor portion.

Alternatively or additionally to any of the embodiments above, the sealmonitoring system may include a collar configured to be coupled to therotatable shaft and rotate with the rotatable shaft, and the senseelement may be disposed on the collar.

In another example, a method of operating a dry gas seal monitoringsystem having a dry gas seal forming a seal between a housing and arotatable shaft is disclosed. The method may include sensing a senseelement rotating with the rotatable shaft, obtaining a signal based onthe sensing of the sense element rotating with the rotatable shaft, anddetermining an axial position of a rotor portion relative to a statorportion based on the signal obtained, the rotor portion and the statorportion form a seal interface of the dry gas seal between the rotatableshaft with which the rotor portion is configured to rotate and astationary housing.

Alternatively or additionally to any of the embodiments above,determining the axial position of the rotor portion relative to thestator portion may be based on an amplitude of the signal obtained.

Alternatively or additionally to any of the embodiments above,determining the axial position of the rotor portion relative to thestator portion may comprise comparing the amplitude of the signalobtained to a threshold value.

Alternatively or additionally to any of the embodiments above,determining the axial position of the rotor portion relative to thestator portion may comprise comparing the amplitude of the signalobtained at a time to amplitudes of the signal obtained at one or moreother times during operation of the dry gas seal.

Alternatively or additionally to any of the embodiments above, thesignal obtained may include one or more pulses and determining the axialposition of the rotor portion relative to the stator portion is based onthe one or more pulses.

Alternatively or additionally to any of the embodiments above, themethod may further include sensing two or more sense elements rotatingwith the rotatable shaft, the two or more sense elements include thesense element, and wherein determining the axial position of the rotorportion relative to the stator portion is based on one or more of anamplitude of the one or more pulses in the signal, a pulse width of theone or more pulses in the signal, and a width between consecutive pulsesin the signal.

Alternatively or additionally to any of the embodiments above, themethod may further include sensing two or more sense elements rotatingwith the rotatable shaft, the two or more sense elements include thesense element, and determining a rotational speed indicative of a speedof the rotatable shaft at speeds below one thousand (1,000) RPMs basedon sensing the two or more sense elements rotating with the rotatableshaft.

Alternatively or additionally to any of the embodiments above, themethod may further include determining when one of a separation of afirst seal face and a second seal face and a contact of the first sealface with the second seal face occurs, associating the rotational speedwith an occurrence of one of the separation of the first seal face fromthe second seal face and the contact of the first seal face with thesecond seal face, and determining an operating condition of the dry gasseal based on the rotational speed associated with the occurrence of oneof the separation of the first seal face from the second seal face andthe contact of the first seal face with the second seal face.

In another example, a dry gas seal is disclosed. The dry gas seal mayinclude a stator portion having a first seal face, a rotor portionhaving a second seal face, wherein the first seal face and the secondseal face are configured to form a seal between a rotatable shaft and astationary housing, a plurality of sense elements configured to rotatein response to rotation of the rotatable shaft, a speed sensor at leastpartially secured relative to the stator portion, the speed sensor isconfigured to sense the plurality of sense elements, and wherein thespeed sensor is configured to sense a rotational speed of the rotatableshaft at speeds below one thousand (1,000) rotations per minute (RPMs)based on sensing the plurality of sense elements and output a signalindicative of an axial position of the rotor portion relative to thestator portion.

Alternatively or additionally to any of the embodiments above, theplurality of sense elements may be configured to be radially spacedcircumferentially around the rotatable shaft.

Alternatively or additionally to any of the embodiments above, theplurality of sense elements are configured to be equally radially spacedcircumferentially around the rotatable shaft.

Alternatively or additionally to any of the embodiments above, one ormore of the plurality of sense elements may be configured to be axiallyspaced from at least one other sense element of the plurality of senseelements.

Alternatively or additionally to any of the embodiments above, theplurality of sense elements may include a plurality of slots.

Alternatively or additionally to any of the embodiments above, a senseelement of the plurality of sense elements may have a cross-sectionalshape that changes along an axial length of the sense element.

Alternatively or additionally to any of the embodiments above, thecross-sectional shape that changes along the axial length of the senseelement may be a circular shape.

Alternatively or additionally to any of the embodiments above, thecross-sectional shape that changes along the axial length of the senseelement may be a trapezoidal shape.

Alternatively or additionally to any of the embodiments above, a senseelement of the plurality of sense elements may include an axiallyextending taper.

Alternatively or additionally to any of the embodiments above, theaxially extending taper may taper at fifty-five (55) degrees relative toa plane perpendicular to an axis of rotation of the rotatable shaft.

Alternatively or additionally to any of the embodiments above, theplurality of sense elements may be disposed on the rotor portion.

Alternatively or additionally to any of the embodiments above, theplurality of sense elements may be disposed on a sleeve of the rotorportion.

Alternatively or additionally to any of the embodiments above, the drygas seal may include a collar configured to be coupled to the rotatableshaft and rotate with the rotatable shaft, and the plurality of senseelements may be disposed on the collar.

Alternatively or additionally to any of the embodiments above, the speedsensor may be a Hall-effect sensor.

Alternatively or additionally to any of the embodiments above, the drygas seal may include a processor configured to receive the signal outputfrom the speed sensor, and the processor is configured to use the signaloutput from the speed sensor to determine the axial position of therotor portion relative to the stator portion. The preceding summary isprovided to facilitate an understanding of some of the innovativefeatures unique to the present disclosure and is not intended to be afull description. A full appreciation of the disclosure can be gained bytaking the entire specification, claims, drawings, and abstract as awhole.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing description of various illustrative embodiments in connectionwith the accompanying drawings, in which:

FIG. 1 is a schematic block diagram of an illustrative seal system ofthe present disclosure;

FIG. 2 is a schematic perspective view of an illustrative dry gas seal;

FIG. 3 is a schematic cross-sectional view of the illustrative dry gasseal of FIG. 2, taken along line 3-3, and as positioned between ahousing and a rotating shaft;

FIG. 4 is a schematic end view depicting an illustrative collar of theillustrative dry gas seal depicted in FIG. 2;

FIG. 5 is a schematic perspective view of an illustrative collar of adry gas seal;

FIG. 6 is a schematic end view of the illustrative collar depicted inFIG. 5;

FIG. 7 is a schematic cross-sectional view of the illustrative collardepicted in FIG. 5, taken along line 7-7;

FIG. 8 is a schematic magnified view of a portion of the illustrativecollar depicted in FIG. 5 that is within circle-8;

FIG. 9 is a schematic cross-sectional view of the illustrative collardepicted in FIG. 5, taken along line 9-9;

FIG. 10 is a schematic sectional view depicting a portion of anillustrative dry gas seal positioned between a housing and a rotatableshaft;

FIG. 11 is a schematic view depicting a speed sensor sensing senseelements and a graph depicting illustrative waveforms of a signal fromthe speed sensor;

FIGS. 12A-12C are schematic views depicting a speed sensor sensing senseelements and graphs depicting illustrative waveforms of a signal fromthe speed sensor;

FIGS. 13A and 13B are schematic views depicting a speed sensor sensingsense elements and graphs depicting illustrative waveforms of a signalfrom the speed sensor; and

FIG. 14 is a schematic flow diagram depicting an illustrative method ofoperating a dry gas seal monitoring system.

While the disclosure is amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit aspect of thedisclosure to the particular illustrative embodiments described. On thecontrary, the intention is to cover all modifications, equivalents, andalternatives falling within the spirit and scope of the disclosure.

DESCRIPTION

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere in thespecification.

All numeric values are herein assumed to be modified by the term“about”, whether or not explicitly indicated. The term “about” generallyrefers to a range of numbers that one of skill in the art would considerequivalent to the recited value (e.g., having the same function orresult). In many instances, the term “about” may include numbers thatare rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numberswithin that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4,and 5).

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, and although the term “and/or” is sometimes expresslyrecited herein, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

It is noted that references in the specification to “an embodiment”,“some embodiments”, “other embodiments”, etc., indicate that theembodiment described may include one or more particular features,structures, and/or characteristics. However, such recitations do notnecessarily mean that all embodiments include the particular features,structures, and/or characteristics. Additionally, when particularfeatures, structures, and/or characteristics are described in connectionwith one embodiment, it should be understood that such features,structures, and/or characteristics may also be used in connection withother embodiments whether or not explicitly described unless clearlystated to the contrary.

The following detailed description should be read with reference to thedrawings in which similar elements in different drawings are numberedthe same. The drawings, which are not necessarily to scale, depictillustrative embodiments and are not intended to limit the scope of theinvention.

Seals are used in a wide variety of applications and/or machinesincluding, for example, gas compressors and other rotating equipmentsuch as gas and steam turbines, turbo expanders, centrifugal pumps andthe like. Such seals are used to seal a rotating interface between ashaft and a housing of a compressor and/or other rotating equipment.Although dry gas seals are primarily discussed herein, it iscontemplated that the disclosed concepts may be applied to other sealsconfigured to seal a rotating interface between a rotating component anda stationary component.

A dry gas seal may include an inboard (IB) seal and an outboard (OB)seal, which may be known as a tandem seal configuration. In such aconfiguration, the IB seal may be generally pressurized to the processsuction pressure, and this process suction pressure may be sufficient tolift the IB seal off statically. The OB seal may be provided as a backupto the IB seal and is designed to withstand a full pressure if the IBseal fails. If there is an issue with either or both of the IB seal orthe OB seals, rubbing of the seal faces may occur and may result inabrasive wear, which is a degenerative process. As the seal wears,damage to the seal faces occurs, the lift off speed increases, and thetouch down speed increases.

In some cases, seal leakage and/or outboard (OB) seal pressure may bemonitored to assess a condition and seal integrity of a dry gas seal.Such monitoring, however, may only be capable of determining when aserious problem or condition with the seal occurs and urgent shut downof the associated equipment is required. As a machine may be required tobe stopped, often immediately with little or no notice of an impendingissue, when a serious problem or condition with the seal occurs, thereis a need to be able to monitor degeneration of a dry gas seal over timeto prevent or mitigate issues resulting in machine down time. Bymonitoring lift off and touch down speed and their variation over time,a good indication of degeneration of sealing faces can be provided,which in turn may give an indication of progressive seal failure suchthat the progressive seal failure can be addressed prior to actual sealfailure and mitigate downtime of the machine. Typical speed monitoringsystems configured to sense operating speeds of a rotatable shaft,however, are not configured to sense the relatively low speeds at whichlift off and touch down occur. Additionally or alternatively, sensing anaxial position and/or axial movement of the dry gas seal over time(e.g., dry gas seals may be configured to move plus or minus three (3)millimeters (mm) or other suitable distance during operation of amachine to which the dry gas seal is applied and such axial movementand/or positioning may be monitored) may be used to avoid, or facilitateavoiding, excessive axial movement in a dry gas seal, where excessiveaxial movement can lead to catastrophic seal failure.

FIG. 1 depicts a schematic block diagram of an illustrative sealmonitoring system 10 that may facilitate establishing and/or determiningseal conditions for dry gas seals and/or other suitable seal systems(e.g., operating conditions for a seal, operational conditions for aseal interface, etc.). The seal monitoring system 10 may include and/ormay be configured to monitor a seal interface of a dry gas seal disposedbetween a rotatable shaft 20 and a stationary housing (not shown in FIG.1). The seal monitoring system 10 may include a controller 12, a sensingmodule 16, and one or more sense elements 44 configured to rotate inresponse to rotation of the rotatable shaft 20. The sensing module 16may be configured to sense one or more parameters related to anoperation of the dry gas seal and output one or more signals to thecontroller 12. In some cases, the sensing module 16 may include a speedsensor 17, an acoustic emissions sensor 19, and/or one or more othersuitable sensors.

In some cases, the sensing module 16 may be secured relative to and/orotherwise stationary relative to a stator portion of the dry gas sealand, in some cases, may be formed as part of the stator portion of thedry gas seal. Alternatively or in addition, at least a portion of thesensing module 16 may be secured relative to a housing component of asystem to which the dry gas seal is applied and/or may be remote fromthe dry gas seal and/or the system to which the dry gas seal is applied.

The sensing module 16 may include the speed sensor 17 to facilitatemonitoring a speed of a rotor portion of the dry gas seal and/or a speedof the rotor portion and/or the rotatable shaft 20. The speed sensor 17may be configured to sense the rotational speed of the rotor portionand/or the rotatable shaft 20 by sensing one or more of the senseelements 44 configured to rotate in response to rotation of therotatable shaft 20. As the one or more sense elements 44 rotate inresponse to rotation of the rotatable shaft 20 and rotate past alocation of the speed sensor 17, the speed sensor 17 may detect thesense elements 44 and output a signal indicative of the speed of therotor portion of the dry gas seal and/or the speed of the rotor portionand/or the rotatable shaft 20. The signal from the speed sensor 17 maybe provided to the controller 12 or other component for furtherprocessing.

In some embodiments, the signal indicative of the speed of the rotorportion and/or the rotatable shaft 20 may also be indicative of an axialposition of the rotor portion and/or the rotatable shaft 20, asdiscussed in greater detail below. In some cases, the signal may be apulsed signal with a pulse sequence indicating an axial position of therotor portion and/or the rotatable shaft 20. Alternatively or inaddition, the signal indicative of an axial position of the rotorportion and/or the rotatable shaft 20 may be a continuous signalincluding pulses or other components indicative of a particular axialposition or location of the rotor portion and/or the rotatable shaft 20.

The speed sensor 17 may be any suitable sensor type that is capable ofsensing a speed of the rotatable shaft 20. For example, the speed sensor17 may include a field sensor, an optical sensor, shaft encoder (e.g.,at an end of the rotatable shaft 20 or other suitable location relativeto the rotatable shaft 20) and/or other suitable type of sensor. Examplefield sensors include, but are not limited to, a magnetic field sensor,a linear variable differential transformer (LVDT), a Hall Effect sensor,and/or other suitable field sensors. In one example, the speed sensor 17may be a Hall Effect sensor, but this is not required.

The acoustic emissions sensor 19, which may be incorporated into thesensing module 16, may be configured to output a signal (e.g., to thecontroller 12 or other component) indicative of an operational conditionof a seal interface of the dry gas seal (e.g., an operational conditionof a first seal face relative to a second seal face). In one example, asa seal face of the dry gas seal rotates with respect to at least oneother seal face of the dry gas seal, the dry gas seal may emit a soundand the sound may change over time as the seal faces separate from oneanother (e.g., during run-up of the seal and/or the system to which theseal is applied) and/or come into contact with one another (e.g., duringrun-down of the seal and/or the system to which the seal is applied),and the acoustic emissions sensor 19 may be configured to sense theemitted sound and provide an indication of when a lift off (e.g.,initial separation of the first seal face and the second seal face afterthe seal faces have been touching) occurs and/or when a touch down(e.g., initial contact between the first seal face and the second sealface as the relative rotation of the seal faces of the dry gas sealslows down) occurs. The acoustic emissions sensor 19 may output a signalindicative of its measurements to the controller 12 for processing(e.g., for processing by a processor 11 and/or other computingcomponent).

The controller 12 may be provided as part of the seal monitoring system10 and may be separate from the sensing module 16, as depicted in FIG.1, or part of the sensing module 16. Alternatively, at least part of thecontroller 12 may be separate from the seal monitoring system 10 and maybe in communication with the sensing module 16. Further, in some cases,at least part of the controller 12 may be located with and/or otherwisebe incorporated in the sensing module 16.

The controller 12 may comprise, among other features, the processor 11,memory 13 (e.g. a non-transitory medium configured to store instructionsfor execution by the processor, data, and/or other information), and/oran input/output (I/O) 15. The I/O 15 may include one or more I/Ointerfaces and may receive signals from the sensing module 16 and thereceived signals may be sent to the memory 13 for storage and/or theprocessor 11 for processing. In some cases, the signal generated by thespeed sensor 17 may be received by I/O 15 and sent to the processor 11.The processor 11 may use that signal to establish an operating conditionof the dry gas seal and/or determine one or more other parameter valuesrelated to the dry gas seal based at least in part on the receivedsignal. In some cases, based at least in part on the signal(s) receivedfrom the speed sensor 17, the processor 11 may be configured todetermine parameter values relating to the dry gas seal including, butnot limited to, a speed of the rotatable shaft 20, an axial position ofthe rotatable shaft 20, a lift off at the seal interface, a lift offspeed, a touch down at the seal interface, a touch down speed, whenmaintenance is needed, an operating condition of the seal interface,and/or other suitable parameter values related to operation of the drygas seal.

The controller 12 may determine an operational condition of the sealinterface of the dry gas seal based on signals from the acousticemissions sensor 19. In some cases, the controller 12 may associate thespeed of the rotor portion of the dry gas seal or the speed of therotatable shaft 20 at a time the signal indicating the operationalcondition of the seal interface occurs. The controller 12 may save theassociation in the memory 13, output the association via the I/O 15 to auser interface, output a control signal (e.g., to the system to whichthe dry gas seal is applied and/or to one or more other suitablecontrollable components), and/or take one or more other suitableactions. In some cases, the outputs from the controller 12 may be basedon a change in speeds associated with the operational condition overtime, speeds associated with the operational condition reaching and/orexceeding a threshold, and/or one or more other factors. In some cases,the operational conditions of the seal interface may be one or both of alift-off occurrence of a first seal face separating from a second sealface during run-up of the dry gas seal and/or the system to which thedry gas seal is applied and a touch-down occurrence of the first sealface touching the second seal face during run-down of the dry gas sealand/or the system to which the dry gas seal is applied.

FIG. 2 depicts a schematic perspective view of an illustrative dry gasseal 22 (e.g., in cartridge form). The dry gas seal 22 may be configuredto form a fluid tight seal between a housing and a rotating shaft. Insome cases, a stator portion 22 a of the dry gas seal 22 (e.g., an outerportion of the dry gas seal 22 depicted in FIG. 2) may be coupled toand/or fixed relative to a housing of a system to which the dry gas seal22 is applied. A rotor portion 22 b of the dry gas seal 22 (e.g., aninner portion of the dry gas seal 22 depicted in FIG. 2) may define anopening 29 for receiving a rotatable shaft (e.g., the rotatable shaft 20depicted in FIG. 1) and may be coupled to the received rotatable shaftand/or otherwise configured to rotate in response to the receivedrotatable shaft when in use as a seal between a stationary housing andthe rotatable shaft.

The dry gas seal 22 may include a collar 48 (e.g., a reluctor ringand/or other suitable collar) having one or more sense elements 44, asdepicted in FIG. 2. Alternatively or in addition, the dry gas seal 22may include one or more other suitable components (e.g., a sleeve orother suitable component) configured to include (e.g., carry, define,etc.) one or more sense elements 44. When included, the collar 48 may beconfigured to connect to one or both of the rotor portion 22 b of thedry gas seal 22 and the rotatable shaft, such that the collar 48 mayrotate in response to rotation of the rotatable shaft. In one example,as depicted in FIG. 2, the collar 48 may be coupled to and/or madeintegral with the rotor portion 22 b via one or more screws 33 and/orother suitable connectors.

The one or more sense elements 44 may be sensed by the speed sensor 17and signals based on the sensed sense elements 44 may be utilized toindicate an axial position of the rotor portion 22 b and/or therotatable shaft 20 and/or a rotational speed of the rotor portion 22 band/or the rotatable shaft 20, as discussed in further detail below. Theone or more sense elements 44 may be configured as slots (as depicted inFIG. 2), protrusions, notches, and/or other configurations suitable forbeing sensed by the sensing module 16. The sense elements 44 may be madefrom any suitable material including, but not limited to, a metalmaterial, a polymer material, a combination of a metal material and apolymer material, and/or other suitable material. In some cases, one ormore of the sense elements 44 may be similar to one or more other senseelements 44 and/or one or more of the sense elements 44 may be differentthan one or more other sense elements 44. In one example of the senseelements 44, the sense elements 44 may be formed into the rotor portion22 b (e.g., via the collar 48 or other suitable component), as shown inFIG. 2. In another example of the sense elements 44, the sense elements44 may be coupled to the rotor portion 22 b via a suitable couplingtechnique including, but not limited to, a screw, a bolt, an adhesive, aweld, a solder connection, a magnetic bond, etc.

As depicted in FIG. 2, the dry gas seal 22 may include a sensor housing31. In some cases, the sensing module 16 may be entirely or at leastpartially coupled to components of the dry gas seal 22 within the sensorhousing 31. Alternatively or in addition, at least part of the sensingmodule 16 may be coupled to other components of the dry gas seal 22without the sensor housing 31. The sensor housing 31 may be coupled toand/or secured relative to the stator portion 22 a of the dry gas seal22, such that the components of the sensing module 16 (e.g., the speedsensor 17) may sense the sense elements 44 rotating in response torotation of the rotatable shaft. The acoustic emissions sensor 19 may becoupled to or relative to the stator portion 22 a of the dry gas seal 22such that the acoustic emissions sensor 19 may be configured to senseoperational conditions of the seal interface. When the sensor housing 31is not included, components of the sensing module 16 may be coupleddirectly to the stator portion 22 a of the dry gas seal 22.

Dry gas seals, such as those commonly applied to gas compressors, mayinclude a single, tandem, or double seal arrangement. Although notrequired, the dry gas seal 22 may have a tandem seal assembly, asdepicted in FIG. 3.

FIG. 3 is a cross-section view taken along line 3-3 of the illustrativedry gas seal 22 shown in FIG. 2 and having a tandem seal assembly, withthe rotatable shaft 20 inserted into the opening 29. During operation,gas present in the process cavity 38, may be sealed from a bearingcavity (not shown) and from the environment by two seals, a first seal24 (e.g., an inboard (IB) seal) and a second seal 26 (e.g., an outboard(OB) seal) arranged in tandem. The components of the first seal 24 andthe second seal 26 may be preassembled into a cartridge, as shown forexample in FIG. 2. When positioned to create a seal between a stationaryhousing and the rotatable shaft 20, the cartridge may include the statorportion 22 a (e.g., a stator) associated with the stationary housing 18and the rotor portion 22 b (e.g., a rotor) associated with the rotatableshaft 20.

In some cases, the rotor portion 22 b may include a sleeve 32 having oneor more portions that are coupled to the rotatable shaft 20 and/orotherwise configured to rotate in response to rotation of the rotatableshaft 20. The sleeve 32 may take on one or more of a variety ofconfigurations and may extend axially beyond the second seal 26, butthis is not required. In some cases, the sleeve 32 may be a singlesleeve component. In other cases, the sleeve 32 may have a plurality ofcomponents or portions. For example, as depicted in FIG. 3, the sleeve32 may have a main sleeve 32 a, a spacer sleeve 32 b, and a lockingsleeve 32 c.

The first seal 24 may form a first seal interface 35 (e.g., an IB sealinterface) defined between a first mating ring 30 (e.g., an IB matingring) connected to the sleeve 32 (e.g., connected to the main sleeve 32a) disposed around the rotatable shaft 20 and having a first seal face,and a first primary ring 28 (e.g., an IB primary ring) connected to thehousing 18 by the stator portion 22 a and having a second seal faceforming the first seal interface 35 with the first seal face of thefirst mating ring 30. The second seal 26 may form a second sealinterface 37 (e.g., an OB seal interface) defined between a secondmating ring 52 (e.g., an OB mating ring) connected to the sleeve 32(e.g., connected to the spacer sleeve 32 b and the locking sleeve 32 c)disposed around the rotatable shaft 20 and having a first seal face anda second primary ring 50 (e.g., an OB primary ring) connected to thehousing 18 by the stator portion 22 a and having a second seal faceforming the second seal interface 37 with the first seal face of thesecond mating ring 52.

Each of the first primary ring 28 and the second primary ring 50 may beaxially movable along a direction substantially coaxial or parallel toan axis of rotation of the rotatable shaft 20 such that a controlleddistance may be maintained along each of the first seal 24 and thesecond seal 26. A spring force may be applied to the first primary ring28 by a first spring 58 (e.g., an IB spring). In some cases, the firstspring 58 may be supported between a first spring carrier 60 (e.g., anIB spring carrier) and a first retainer 62 (e.g., an IB retainer) of thestator portion 22 a of the dry gas seal 22. A spring force may beapplied to the second primary ring 50 by a second spring (59) e.g., anOB spring). In some cases, the second spring 59 may be supported betweena second spring carrier 61 (e.g., an OB spring carrier) and a secondretainer 63 (e.g., an OB retainer) of the stator portion 22 a of the drygas seal 22. Although the first retainer 62 and the second retainer 63are depicted in FIG. 3 as separate components, the first retainer 62 andthe second retainer 63 may be a single component (e.g., a singleretainer) that performs the functions of the first retainer 62 and thesecond retainer 63.

As depicted in FIG. 3, the first mating ring 30 and the second matingring 52 may be configured to rotate with the rotatable shaft 20. Thefirst primary ring 28 and the second primary ring 50 may be axiallyadjustable within the stator portion 22 a, while also being rotationallyfixed relative to the stationary housing 18. The mating rings 30 and 52,and the primary rings 28 and 50, however, may be configured in differentrelative configurations including, but not limited to, the primary rings28 and 50 rotating with the rotatable shaft 20 and the mating rings 30and 52 remaining rotationally fixed relative to the primary rings 28 and50. Further, in alternative configurations the dry gas seal 22 may havea single seal configuration or a double seal configuration, rather thanthe tandem seal configuration depicted in the Figures. Further, althoughthe first seal 24 refers to the IB seal and the second seal 26 refers tothe OB seal as described herein, the terms first and second are used fordescriptive purposes only and the OB seal may be a first seal and the IBseal may be a second seal.

The arrangement and materials used for these seals can be optimizedbased on the application, for example, the operating pressures of thegas, as well as the chemical composition of the gas and/or the operatingenvironment of the machine. The radial seals may include O-rings, othercomposite seal arrangements, such as advanced polymer seals surroundingseal carrier members, or other suitable types of materials for seals.

The dry gas seal 22 may further include the sensing module 16, asdepicted in FIG. 3. As discussed above, in reference to FIG. 1, thesensing module 16 may be configured to sense one or more parametersrelated to the dry gas seal 22 and/or the rotatable shaft 20 via one ormore sensors (e.g., the speed sensor 17, the acoustic emissions sensor19 (not depicted in FIG. 3), and/or one or more other sensors or othercommunication components). The sensing module 16 may be coupled toand/or coupled relative to the stator portion 22 a of the dry gas seal22 and, in some cases, at least a portion of the sensing module 16 maybe formed as part of the housing of the dry gas seal 22. Alternativelyor in addition, it is contemplated that at least part of the sensingmodule 16 may be a separate component in communication with the housingof the dry gas seal and/or may be mounted at a location independent ofthe housing of the dry gas seal 22. In some cases, the housing 31 of thesensing module 16 may be secured relative to the housing of the dry gasseal 22.

As discussed with reference to FIG. 1, the sensing module 16 may includethe speed sensor 17 to facilitate monitoring the dry gas seal 22. Thespeed sensor 17 may be configured to sense a rotational speed of therotatable shaft 20 by sensing one or more sense elements 44 configuredto rotate in response to rotation of the rotatable shaft 20. As the oneor more sense elements 44 rotate past a location of the speed sensor 17,the speed sensor 17 may sense each sense element 44, and the sensingmodule 16 may generate a signal, which may be indicative of a speed ofthe rotatable shaft 20 and/or the rotor portion 22 b of the dry gas seal22. When connected to the controller 12, the sensing module 16 mayoutput the signal to the controller 12.

When the speed sensor 17 includes a Hall Effect sensor, the Hall Effectsensor may be a transducer that varies its output voltage in response toa magnetic field. The Hall Effect sensor depicted in FIG. 3 may includea magnet 64 and a sensor integrated circuit (IC) 66 in communicationwith one or more components on a printed wiring board or printed circuitboard (PCB) 68 connected to one or more connectors 70. In operation, theHall Effect sensor may function by providing a voltage across the sensorIC 66 and applying a magnetic field to the sensor IC 66 with the magnet64, such that a voltage output from the sensor IC 66 depends on themagnetic field. Then, as the sense elements 44 pass the speed sensor 17,the magnetic field produced by the magnet 64 may be modified and theoutput voltage of the sensor IC 66 may change from an output voltagewhen a sense element 44 is not being sensed. The output voltage from thesensor IC 66 may be provided to the PCB 68 and the signal may be outputfrom the PCB 68 and sent through the connector(s) 70 to the controller12 and/or other computing component. Although the Hall Effect sensor ofFIG. 3 is depicted and described, other configurations of Hall Effectsensors and speed sensors 17 are contemplated.

Although the controller 12 is depicted in FIG. 3 as being spaced fromthe housing 31 of the sensing module 16 by the connectors 70, thecontroller 12 may be incorporated into the sensing module 16 and/orconnected to the sensing module 16 by one or more connectors other thanthe connectors 70. The connectors 70 depicted in FIG. 3 areschematically depicted and, when included, may be any suitable type ofelectrical and/or mechanical connectors. Example electrical and/ormechanical connectors include wired connectors, wireless connectors,Bluetooth connectors, USB connectors, USB-c connectors, two-prongconnectors, three-prong connectors, HDMI connectors, and/or othersuitable connectors.

As depicted in FIG. 3, the speed sensor 17, a portion of the sensingmodule 16, and the sense elements 44 may be mounted adjacent an ambientside of the dry gas seal 22 (e.g., as opposed to the process side of thedry gas seal 22 adjacent the process cavity 38). Alternatively or inaddition, at least a portion of the sensing module 16 and/or the senseelements 44 may be located at one or more other suitable locations. Inone example, the sensing module 16 or at least a portion of the sensingmodule 16 and the sense elements 44 may be mounted or otherwisepositioned at any suitable location relative to one another such thatthe sensing module 16 may be capable of sensing the sense elements 44 asthe sense elements 44 rotate relative to rotation of the rotatable shaft20. Further, when the sensing module 16 includes the acoustic emissionssensor 19, the sensing module 16 may be mounted or otherwise positionedat a suitable location for sensing acoustic emissions from the dry gasseal 22. The speed sensor 17 and the acoustic emissions sensor 19 may belocated within the housing 31 of the sensing module 16 at a singlelocation or within the housing 31 of the sensing module 16 at spacedapart locations, where the housing 31 may comprise a plurality ofsub-components spaced from one another and configured to housecomponents of the sensing module 16.

As discussed above, the sensing module 16 may comprise the acousticemissions sensor 19. The acoustic emissions sensor 19 may be configuredto output a signal to the processor 11 indicating an operationalcondition of the first seal face relative to the second seal face (e.g.,an operational condition of the dry gas seal 22). For example, theacoustic emissions sensor 19 may be configured to sense sounds made bythe dry gas seal 22 as the dry gas seal 22 changes operationalconditions and output a signal that changes as detected sound changes.The operational conditions of the dry gas seal 22 may be a lift off ofthe seal faces (e.g., separation of the seal faces) of the mating rings30, 52 and the primary rings 28, 50 during run up of the dry gas seal 22or system to which the dry gas seal 22 is applied and/or a touchdown ofthe seal faces (e.g., contact between the seal faces) of the matingrings 30, 52 and the primary rings 28, 50 during run down of the dry gasseal 22 or system to which the dry gas seal 22 is applied. In somecases, the acoustic emissions sensor 19 may output a signal indicativeof its measurements to the controller 12 (e.g., to the processor 11 ofthe controller 12 or other suitable processor) for processing.

The acoustic emissions sensor 19 may be any suitable type of acousticemissions sensor that is capable of sensing sound from a seal interface(e.g., the seal interfaces 35 and 37) and outputting a signal indicativeof a sensed sound. In some cases, the acoustic emissions sensor 19 maybe configured to output the same signal independent from which sealinterface a detected sound is coming from when the dry gas seal 22includes more than one seal interface, such as the first seal interface35 and the second seal interface 37, and/or one or more other suitableseal interfaces. Alternatively or in addition, the acoustic emissionssensor 19 may be configured to output different signal values for eachseal interface or a group of seal interfaces when the dry gas seal 22includes more than one seal interface. Based, at least in part, onoutputs from the acoustic emissions sensor 19, the acoustic emissionssensor 19 and/or the controller 12 may be utilized to determine theoperational conditions of each seal interface 35, 37 of the dry gas seal22.

The controller 12 may determine the operational condition of the dry gasseal 22 (e.g., the first seal face relative to a second seal face of aseal interface 35, 37) based on the signal from the acoustic emissionssensor 19. Alternatively or in addition, the acoustic emissions sensor19 may be configured to determine the operational condition of the drygas seal 22. In some cases, the operational condition of the rotatableshaft 20 and/or the dry gas seal 22 may be determined by comparing anacoustic emissions signal to one or more threshold values. In oneexample, when the operational conditions of the dry gas seal 22 to bedetermined are a lift off operational condition and a touch downoperational condition, the acoustic emissions signal may be compared toa lift off threshold value and a touch down threshold value. If theacoustic emissions signal reaches or goes beyond the lift off thresholdvalue, the controller 12 or the acoustic emissions sensor 19 mayindicate the dry gas seal 22 has reached a lift off operationalcondition (e.g., a first seal face and a second seal face of at leastone of the seal interfaces 35, 37 have separated). If the acousticemission signal reaches or goes beyond the touch down threshold value,the controller 12 or the acoustic emissions sensor 19 may indicate thedry gas seal 22 has reached a touch down operational condition (e.g., afirst seal face and a second seal face of at least one of the sealinterfaces 35, 37 have touched).

As discussed in greater detail below, the controller 12 may beconfigured to associate a speed of the rotor portion 22 b of the dry gasseal 22 or a speed of the rotatable shaft 20 with an occurrence of anoperational condition of the dry gas seal 22. Further, the controller 12may be configured to store the speed as associated with the occurrenceof the operational condition in memory 13 and/or other suitable memory.In some cases, the controller 12 may be configured to output the speedas associated with the occurrence of the operational condition to one ormore other computing systems including, but not limited to, a remoteserver, a user interface and/or other suitable computing system.Additionally or alternatively, the controller 12 may be configured tomonitor the speeds associated with occurrences of the operationalconditions of the dry gas seal 22 to determine an operating condition ofthe dry gas seal that may be used to monitor a health of the dry gasseal 22, diagnose conditions of the dry gas seal 22, detect anomalousseal operating conditions that may lead to failure or damage ofcomponents of the dry gas seal 22, etc.

FIG. 4 depicts a schematic end view of the collar 48 having a pluralityof sense elements 44 along an outer axial surface of the collar 48 and aplurality of holes 45 for receiving bolts or screws 33 (see FIG. 2). Thesense elements 44 may be disposed on the collar 48 such that the senseelements 44 are configured to be radially spaced (e.g., with equalspacing between each sense element 44 and another sense element 44 ornon-equal spacing between two consecutive sense elements 44 and at leastone other set of two sense elements) circumferentially around therotatable shaft 20 when the collar 48 is positioned around the rotatableshaft 20. The term “disposed on” an element as used herein may includeon top of an element, in an element, formed monolithically with, in, oron the element, and/or coupled with or to the element so as to be in,on, or of the element.

As depicted, the sense elements 44 may be slots 46 which have aconsistent shape along its axial length (e.g., where the axial length isparallel to a center axis of the collar 48). However, the sense elements44 may be protrusions, indents, and/or have one or more other suitableshapes including, but not limited to, hole configurations, circleshapes, trapezoidal shapes, shapes that have a cross-sectional shapehaving a surface with a depth relative to a sensor (e.g., the speedsensor 17 or other suitable sensor) that changes over an axial length ofthe sense element (e.g., where the depth relative to the sensor thatchanges may be an axial taper in the surface or other change in depthbetween the surface and the sensor), shapes with one or more taperedsurfaces, etc. Although the sense elements 44 in FIG. 4 are depicted ashaving a same shape as all other sense elements 44, one or more of thesense elements 44 may have a different shape or configuration than atleast one other sense element 44.

The dry gas seal 22 may include a suitable number of sense elements 44to facilitate sensing accurate rotational speeds of the rotatable shaft20 and/or the rotor portion 22 b of the dry gas seal 22 at low speeds atwhich a separation or contact of seal faces forming the seal interfaces35, 37 occurs. Such low speeds of the rotatable shaft 20 and/or therotor portion 22 b of the dry gas seal 22 may include speeds less thanabout one thousand (1,000) RPMs, lest than about five hundred (500)RPMs, and/or other suitable similarly low speeds.

Although it may be known to sense speeds of rotatable shafts used incompressors and/or other equipment using a single sense element, suchspeeds to be sensed are much faster than speeds at which changes inoperational conditions of first and second seal faces relative to oneanother occur. Thus, it has been found that in order to provide accuratespeeds measurements at low speeds, a plurality of sense elements may beused to achieve a desired resolution in the speed sensed by the speedsensor 17. For example, when a single sense element is used to sensespeeds from about ten thousand (10,000) RPMs to about forty thousand(40,000) RPMs or higher, which is a typical range of operating speeds ofthe rotatable shaft 20, the single sense element is sensed within arange of about every 0.0015 seconds to about 0.0060 seconds over theprovided range of sensed speeds. Thus, to achieve a desired latencyperiod between sensed sense elements at low speeds, more than a singlesense element is needed. It has been found that two or more senseelements 44 that are sensed by the speed sensor 17 may provide a speedsignal with desirable latency period between sensed sense elements 44.In one example, as depicted in FIG. 4, eighteen (18) sense elements 44are provided. When eighteen (18) sense elements 44 are provided andspeed is to be sensed at low speeds within a range from about ten (10)RPMs to about one thousand (1,000) RPMs, there may be a latency periodbetween sensed sense elements 44 from about 0.0033 seconds to about0.3333 seconds. Although eighteen (18) sense elements 44 are used in theexample of FIG. 4, other suitable number of sense elements 44 may beutilized including, but not limited to, two (2) sense elements, four (4)sense elements, six (6) sense elements, eight (8) sense elements, ten(10) sense elements, twelve (12) sense elements, fifteen (15) senseelements, eighteen (18) sense elements, twenty five (25) sense elements,thirty (30) sense elements and/or other suitable sense elements. In somecases, a number of sense elements may be selected based, at least inpart, on balancing a desire to have a shorter latency period betweensensed sense elements 44 and a size (e.g., circumference, etc.) of thecollar, sleeve, or other component at which the sense elements 44 may bepositioned.

FIGS. 5-9 depict various schematic views of sense elements 44 disposedon an illustrative collar 48, where the sense elements 44 taper in anaxial direction. FIG. 5 is a schematic perspective view of the collar 48with sense elements 44 formed from a slot 46 and having an axiallytapered cross-section (e.g., a cross-sectional shape that changes alongan axial length of the sense element 44). FIG. 6 is an end view of thecollar 48 depicted in FIG. 5. As shown in FIGS. 5 and 6, the collar 48may include fifteen (15) sense elements 44 formed from slots 46 with anaxially tapered cross-section, but more than fifteen (15) sense elements44 or less than fifteen (15) sense elements may be used, as desired.Although the sense elements are shown as being equally radially spacedabout a circumference of the collar 48 and configured to be similarlydisposed around the rotatable shaft 20, this is not required in allcases.

As depicted in FIG. 6, one or more of the sense elements 44 may includea notch 47 or other suitable marking that may be sensed by the speedsensor 17. In some cases, the notch 47 may be positioned radiallyoff-centered on the sense element 44 (e.g., the notch 47 may be at oneedge of the slot 46 of the sense element 44, as depicted in FIG. 6),such that the speed sensor 17 may sense the notch 47 of the senseelement 44 and a resulting signal in response to sensing the senseelements 44 may be indicative of a direction of rotation (e.g.,clockwise or counter clockwise) of the rotatable shaft 20 and/or therotor portion 22 b of the dry gas seal 22. For example, when therotatable shaft 20 and/or the rotor portion 22 b of the dry gas seal 22is rotating in a first direction, the sensed notch 47 may be representedin a signal of speed sensor 17 immediately before a represented slot 46of the sense element 44 and the sensed notch 47 may be represented in asignal of the speed sensor 17 immediately after a represented slot 46 ofthe sense element 44 when rotating in a second direction that isopposite the first direction.

To facilitate identifying the notch 47 within a signal from the speedsensor 17 and/or for other suitable purposes, the notch 47 may beincluded in less than all of the sense elements 44. For example, thenotch 47 may be located in one and only one sense element 44, everyother sense element 44, every third sense element 44, ever fourth senseelement 44, every fifth sense element 44, every sixth sense element 44,and/or at other suitable intervals or arrangements. As depicted in FIG.6, the notch 47 may be located in every fifth sense element 44. In somecases, the notch 47 may be located in all of the sense elements 44.

The notch 47 may have any suitable size for detection by the speedsensor 17 and/or identification within a signal from the speed sensor17. In some cases, the notch 47 may extend a radial distance (e.g., awidth) between two adjacent sense elements 44 any suitable distance aslong as the notch 47 is not symmetrical (e.g., is asymmetrical) about aradial midway point between the two adjacent sense elements 44. In oneexample, the notch 47 may have a radial distance that is greater thanhalf of a radial distance between the two adjacent sense elements 44,less than half of the radial distance between the two adjacent senseelements 44, or equal to the radial distance between the two adjacentsense elements 44. In one example, the notch 47 may extend a radialdistance of about six (6) radial degrees, but this is not required andother radial distances are contemplated. The notch 47 may have anysuitable depth. In some cases, a depth of the notch 47 may be greaterthan, less than, or equal to a depth of an adjacent (e.g., nearest)sense element 44. The depth of the notch 47 may be consistent or varyalong a length and/or height of the notch 47.

An ability to detect a direction of rotation of the rotatable shaft 20and/or the rotor portion 22 b may facilitate preventing premature sealfailure. Typical speed monitors that are used to detect speeds ofrotating parts (e.g., rotating parts of turbomachines or other suitablerotating parts) cannot determine if a shaft rotates backwards,particularly at low speeds. With the disclosed system being capable ofdetecting low speeds and a direction of rotation of the rotatable shaft20 and/or the rotor portion 22 b, low speed reverse rotation (e.g.,which may be caused by valve or seal leakage) may be detected andidentified to prevent or to facilitate preventing premature seal failureby allowing users to address any valve or seal leakage before sealfailure.

FIG. 7 is a schematic cross-sectional view of the collar 48 taken alongline 7-7 in FIG. 6. As depicted in FIG. 7, the slot 46 of the senseelement 44 may be axially tapered (e.g., the slot 46 may taper in anaxial direction). The taper of the slot 46 may be tapered at anysuitable angle A (e.g., any suitable angle A relative to a planeextending perpendicular to an axis of rotation of the rotor portion 22b, the collar 48, and/or the rotatable shaft 20). In some cases, thetaper of the slot 46 may be tapered at an angle that facilitates thespeed sensor 17 outputting a different signal value (e.g., a differentvoltage amplitude or other suitable signal value type) based on an axialposition of the sense element, which in turn may be indicative of arelative axial position of the seal faces forming the seal interfaces35, 37, as discussed in greater detail below. Example angles for theangle A of the axially tapered slot 46 may be an angle from about five(5) degrees to about eighty five (85) degrees, from about fifteen (15)degrees to about seventy five (75) degrees, from about thirty five (35)degrees to about sixty five degrees (65), from about forty five (45)degrees to about fifty five (55) degrees, and/or at one or more othersuitable angles. In one example, the angle A of the axially tapered slot46 may be at about fifty five (55) degrees.

FIG. 8 schematically depicts an enlargement of a portion of theillustrative collar 48 that is within circle 8 depicted in FIG. 6. Theenlarged portion of the collar 48 in FIG. 8 provides an exampleconfiguration of the notch 47. In the example depicted and as discussedabove, the notch 47 of the sense element 44 may be positioned at theouter most axial and/or radial edge of the slot 46. The notch 47 may besensed by the speed sensor 17, and due at least in part to the positionof the notch 47, a direction the rotatable shaft 20 and/or the rotorportion 22 b of the dry gas seal is rotating may be determined (e.g., bythe controller 12) from the signal that is output by the speed sensor17.

The notch 47 may take on any suitable 2-dimensional and/or 3-dimensionalshape. As shown in FIG. 8, from an end view, the notch 47 may have agenerally rectangular shape, but this is not required and the notch 47,from an end view, may take on one or more other shapes configured tofacilitate detection by the speed sensor 17, facilitate determining adirection of rotation of the rotatable shaft 20 and/or the rotor portion22 b of the dry gas seal, facilitate forming the notch 47, and/orfacilitate one or more other suitable functions. In some cases, thenotch 47 may have a different profile and/or configuration than theslots 46 of the sense element 44 to facilitate identifying sensednotches 47 in the signal from the speed sensor 17.

FIG. 9 is a schematic cross-sectional view of the collar 48, taken alongline 9-9 of FIG. 6. As depicted in FIG. 9, the notch 47 of the senseelement 44 may be axially tapered. The taper of the notch 47 may betapered at any suitable angle B and may have a depth that is offset froma surface of the taper of the slot 46 such that the notch 47 may bedistinguishable from the slot 46 based on the signal from the speedsensor 17. The taper of the notch 47 may be tapered such that thetapered portion of the notch 47 may run generally parallel to thetapered portion of the slot 46 (e.g., such that angle A may be aboutequal to angle B), but this is not required. In some cases, the angle Bof the axially tapered notch 47 may be an angle from about five (5)degrees to about eighty five (85) degrees, from about fifteen (15)degrees to about seventy five (75) degrees, from about thirty five (35)degrees to about sixty five degrees (65), from forty five (45) degreesto about fifty five (55) degrees, and/or at one or more other suitableangles. In one example, the angle B of the axially tapered slot 46 maybe at about fifty five (55) degrees.

FIG. 10 depicts a cross-sectional view of the dry gas seal 22 with therotatable shaft 20 inserted within the opening 29 of the dry gas seal 22that is similar to the view depicted in FIG. 3, but with the senseelements 44 located on the sleeve 32 (e.g., the locking sleeve 32C, asdepicted in FIG. 10, but this is not required) of the rotor portion 22 bof the dry gas seal 22 and with the collar 48 omitted. Although thecollar 48 is omitted from the dry gas seal 22 of FIG. 10, the collar 48may be included even when the sleeve 32 includes one or more senseelements 44.

As depicted in FIG. 10, the sleeve 32 may extend outward toward anambient space or away from the process cavity 38 such that a portion ofthe sleeve 32 faces the sensing module 16 (e.g., faces the sensor IC66). The sense elements 44 in the sleeve 32 of the dry gas seal 22 maybe located at an end of the sleeve 32, similar to how the sense elements44 are depicted in FIGS. 4-9 as being at a top end of the collar 48, orspaced from the end of the sleeve 32 as depicted in FIG. 10. Further,the sense elements 44 may be formed by the slot 46 and/or take on one ormore other suitable shapes or configurations. In some cases, the senseelement 44 within the sleeve 32 may take on configurations similar to ordifferent than the configurations of other sense elements 44 describedherein.

As referred to above, it may be possible to determine an axial positionof a portion of the dry gas seal 22 (e.g., an axial position of therotor portion 22 b and/or other suitable portion of the dry gas seal 22)and/or axial movement of the dry gas seal 22 (e.g., axial movement ofthe rotor portion 22 b relative to the stator portion 22 a, and/ormovement of one or more other portions of the dry gas seal 22) based, atleast in part, on a signal 72 from the speed sensor 17. FIG. 11 depictsa schematic illustrative graph of a signal 72 output from the speedsensor 17 (e.g., as depicted in schematic form in FIG. 11) sensing senseelements 44 (e.g., sense elements 44 a-44 d) with an axial taper similarto the sense elements 44 in FIGS. 5-9. The graph depicts time on thex-axis and amplitude in voltage (e.g., an amplitude of the signal 72from the speed sensor 17) on the y-axis, from which an axial positionand/or movement of the dry gas seal 22, or portions thereof, may bedetermined (e.g., determined by the speed sensor 17, the controller 12,and/or other computing device). Although an amplitude in voltage of thesignal 72 is depicted in FIG. 11, other measurements of the signal 72may be monitored over time to determine axial positions and/or axialmovement of the dry gas seal 22. Such signals 72 from the speed sensor17 used to and/or monitoring of the signals 72 to determine axialpositions and/or movement of the dry gas seal 22 (or portions thereof)may be utilized to identify thermal distortion at the seal interface(s)of the dry gas seal 22, lift off and touch down at the seal interface(s)of the dry gas seal 22 (assuming movement can be detected at a desiredresolution), expected leakage of the dry gas seal 22, when to performmaintenance on the dry gas seal 22, and/or determine one or more othersuitable conditions of the dry gas seal 22. It is contemplated thatwhile still capable of being used for the functional purposes discussedherein, graphs of the signal 72 may take on one or more other formsbased on particular configurations and/or arrangements of the senseelements 44 and/or based on possible types of measurements of the signal72.

In FIG. 11, the sense elements 44 are depicted as being disposed on, foran example, the collar 48 and the collar 48 is depicted in two differentaxial positions representing axial positions of the dry gas seal 22 andaxial movement of the dry gas seal 22. At a first axial position of thecollar 48 depicted in FIG. 11, the speed sensor 17 senses a top or topportion of the tapered slot 46 (e.g., at a distance D1 from the speedsensor 17), which is a portion of the sense element 44 that is fartheraway from the speed sensor 17 than the bottom of the tapered slot 46. Ata second axial position of the collar 48 depicted in FIG. 11, the speedsensor 17 senses a bottom or bottom portion of the tapered slot 46(e.g., at a distance D2 from the speed sensor 17, where the distance D2is less than the distance D1), which is a portion of the sense element44 that is closer to the speed sensor 17 than the top of the taperedslot 46. The tapered nature of the sense element 44 (e.g., the taperedslot 46) is shown in a broken line indicating the tapered sense element44 may not actually be viewable from the angle depicted in FIG. 11.Additionally, the broken line extending from the speed sensor 17 to thesense element 44 is shown for illustrative purposes only and a viewableline may or may not actually be used by the speed sensor 17 to determinea distance from the speed sensor 17 to the sense element 44.

As the speed sensor 17 senses the sense elements 44 of the collar 48over time, the speed sensor 17 outputs the signal 72 with amplitudesvarying over time based on an axial position of the dry gas seal 22. Thesignal 72 may have an amplitude, A1, as depicted schematically in FIG.11 with spikes or pulses 44 a″ and 44 b″ in the graph of the signal 72,when the sensor 17 senses the sense elements 44 (e.g., sense elements 44a, 44 b) with the collar 48 at the first axial position. When the speedsensor 17 senses the sense elements 44 (e.g., sense elements 44 c, 44 d)with the collar 48 at the second axial position in FIG. 11, the speedsensor 17 may output signals 72 having an amplitude, A2, as depictedschematically in FIG. 11A with spikes or pulses 44 c′, 44 d″ in thegraph of the signal 72. As depicted in FIG. 11, the amplitude, A1, ofthe signal 72 when the sense elements 44 (e.g., the sense elements 44 a,44 b) are sensed with the collar 48 at the first axial position isgreater than the amplitude, A2, of the signal 72 when the sense elements44 (e.g., the sense elements 44 c, 44 d) are sensed with the collar 48at the second axial position, where the change in amplitude may bedetermined to be indicative of an axial position of the rotor portion 22b of the dry gas seal 22 (e.g., a position relative to the statorportion 22 a or relative to a position of one or more other componentsof the dry gas seal 22) and/or an amount of axial movement of the rotorportion 22 b. Although amplitudes of the signal 72 are only depicted inFIG. 11 for sensed positions of the collar 48 at two axial positions,the speed sensor 17 may output signals 72 with amplitudes at levels lessthan, greater than, and/or between those depicted in FIG. 11 for axialpositions of the collar 48 outside of and/or between the axial positionsof the collar 48 depicted in FIG. 11.

Based, at least in part, on the signals 72 from the speed sensor 17, thecontroller 12 (e.g., via the processor 11 thereof, program code storedin the memory 13, and/or other suitable computing components) may beable to determine a status or condition of the dry gas seal 22 (e.g.,the operational condition at a seal interface of the dry gas seal 22,the operating condition of the dry gas seal 22, etc.). In one example,the controller 12 may associate speeds of the rotor portion 22 a of thedry gas seal 22 as sensed by the speed sensor 17 or other suitable speedsensor with sensed amplitudes of the signal and compare changes in,trends in, and/or other analyses of amplitudes and/or speeds at variousamplitudes of the signal 72 over time to determine and/or identify astatus or condition of the dry gas seal 22. Alternatively oradditionally, the signal 72 indicative of sensing the sense elements 44(e.g., the sense elements 44 a, 44 b, 44 c, 44 d, etc.) may beconsidered to be or to include spikes or pulses (e.g., spikes or pulses44 a′, 44 b′, 44 c′, 44 d′, etc.) in the signal 72 and the controller 12may compare values related to the pulses (e.g., amplitudes of thepulses, widths of the pulses, width of spaces between pulses (e.g., awidth of spaces between consecutive pulses), speeds associated with thepulses, etc.) in the signal 72 to threshold values or a look up table orenter the values related to the pulses into an algorithm to determine anaxial position or an amount of axial movement of the collar 48, the drygas seal 22, the rotor portion 22 a relative to the stator portion 22 b,and/or the rotatable shaft 20.

Although the example of determining an axial position and/or axialmovement of the dry gas seal 22 and/or an operational condition of afirst seal face relative to a second seal based at least in part on theoutput signal 72 from the speed sensor 17 is provided using the taperedslots 46 depicted in FIGS. 5-9, an axial position and/or movement of thedry gas seal 22 (e.g., the rotor portion 22 b relative to the statorportion 22 a), or portions thereof, may be determined using any suitableslot configuration that varies vertically and results in the speedsensor 17 outputting different signals 72 (e.g., signals with differentamplitudes, different pulse widths, and/or other suitable differences)as portions of the dry gas seal 22 move axially. In one example, anaxial position of the dry gas seal 22, or portions thereof, may bedetermined using a slot 46 for a sense element 44 that has a curvedcross-section, a sense element 44 with a circular cross-section, a senseelement 44 with a trapezoidal cross-section, a sense element 44configured to extend an extended portion or an entirety of acircumference around a rotatable shaft with varying depth at varyingaxial positions, and/or sense elements 44 with other suitableconfigurations and/or cross-sections.

FIGS. 12A-13B depict additional or alternative configurations of thesense elements 44 disposed on a collar 48, along with graphs of thesignal 72 output at various axial positions of the collar 48. AlthoughFIGS. 12A-13B depict example configurations of sense elements 44, otherconfigurations are contemplated. Although the sense elements 44 in FIGS.12A-13B are disposed on the collar 48, similar or alternative senseelements 44 may be disposed on other portions of the rotor portion 22 bof the dry gas seal 22 and/or may be otherwise disposed to rotate aroundan axis of rotation of the rotatable shaft 20.

FIGS. 12A-12C depict sense elements 44 having circle shapes orconfigurations (e.g., a shape or configuration having a cross-sectionalshape that changes along an axial length of the sense element 44), wheresome of the sense elements 44 have different diameters than other senseelements 44, some of the sense elements 44 are axially spaced and/oroffset from other sense elements 44, some of the sense elements 44 areradially spaced and/or offset from other sense elements 44, some of thesense elements 44 are axially and radially spaced and/or offset fromother sense elements 44, and all of the sense elements 44 have aconstant and same depth. FIG. 12A depicts the speed sensor 17 (shown inschematic form in FIGS. 12A-12C) sensing the sense elements 44 disposedon the collar 48, where the collar 48 is at a first axial positionrelative to the speed sensor 17. The speed sensor 17 may output thesignal 72 and the pulses depicted in the graph of FIG. 12A may beindicative of sensing the sense elements 44. As depicted in FIG. 12A,the pulses in the signal 72 take on a pattern that is aligned with thepattern of the sensed sense elements 44, where the pulses have aconsistent width that is aligned with a width of the sensed senseelements 44, a consistent width or spacing between pulses that isaligned with a width or spacing of the sensed sense elements 44, and aconsistent amplitude, A, (e.g., where the consistent amplitude may bedue to the constant and consistent depth of the sense elements 44 thatare sensed).

FIG. 12B depicts the speed sensor 17 sensing the sense elements 44disposed on the collar 48, where the collar 48 is at a second axialposition relative to the speed sensor 17 and the sense elements 44 havea different pattern than the pattern of the sense elements 44 at thefirst axial position of the collar 48 relative to the speed sensor 17.The speed sensor 17 may output the signal 72 and the pulses depicted inthe graph of FIG. 12B may be indicative of sensing an axial position ofthe sense elements 44 at the second axial position of the collar 48. Asdepicted in FIG. 12B, the pulses in the signal 72 take on a pattern thatis aligned with the pattern of the sensed sense elements 44, where thepulses have a consistent width that is aligned with a portion of thesensed sense elements 44, a consistent width or spacing between pulsesthat is aligned with a width or spacing between the sensed senseelements 44, and a consistent amplitude, A, (e.g., where the consistentamplitude may be due to the constant and consistent depth of the senseelements 44 that are sensed).

FIG. 12C depicts the speed sensor 17 sensing the sense elements 44disposed on the collar 48, where the collar 48 is at a third verticalposition relative to the speed sensor 17 and the sense elements 44 havea different pattern than the pattern of the sense elements 44 at thefirst axial position and the second axial position of the collar 48relative to the speed sensor 17. The speed sensor 17 may output thesignal 72 and the pulses depicted in the graph of FIG. 12C may beindicative of sensing an axial position of the sense elements 44 at thethird axial position of the collar 48. As depicted in FIG. 12C, thepulses in the signal 72 take on a pattern that is consistent with thepattern of the sensed sense elements 44, where the pulses have a widthconsistent with a portion of the sensed sense elements 44 (e.g., wherethe width of the pulses vary with a width or diameter of the senseelements 44), a consistent width or spacing between pulses that isconsistent with a width or spacing between the sensed sense elements 44,and have a consistent amplitude, A, (e.g., where the consistentamplitude may be due to the constant and consistent depth of the senseelements 44 that are sensed).

FIGS. 13A and 13B depict sense elements 44 having a trapezoidal shape orconfiguration (e.g., a shape or configuration having a cross-sectionalshape that changes along an axial length of the sense element 44), whereeach sense element 44 has the same or similar dimensions as the othersense elements 44. FIG. 13A depicts the speed sensor 17 (shown inschematic form in FIGS. 13A and 13B) sensing the sense elements 44disposed on the collar 48, where the collar 48 is at a first axialposition relative to the speed sensor 17. The speed sensor 17 may outputthe signal 72 and the pulses (e.g., increases in amplitude of the signal72) depicted in the graph of FIG. 13A may be indicative of sensing anaxial position of the sense elements 44 at the first axial position ofthe collar 48. As depicted in FIG. 13A, the pulses in the signal take ona pattern than is consistent with the pattern of the sensed senseelements 44, where the pulses have a consistent width that is alignedwith a width of the sensed sense elements 44, a consistent width orspacing between pulses that is aligned with a width or spacing of thesensed sense elements 44, and a consistent amplitude, A, (e.g., theconsistent amplitude may be due to the constant and consistent depth ofthe sense elements 44 that are sensed).

FIG. 13B depicts the speed sensor 17 sensing the sense element 44disposed on the collar 48, where the collar 48 is at a second axialposition relative to the speed sensor 17 and the sense elements 44 havea different pattern than the pattern of the sense elements 44 at thefirst axial position of the collar 48 relative to the speed sensor 17.The speed sensor 17 may output the signal 72 and the pulses (e.g.,increases in amplitude of the signal 72) depicted in the graph of FIG.13B may be indicative of sensing an axial position of the sense elements44 at the second axial position of the collar 48. As depicted in FIG.13B, the pulses in the signal 72 take on a pattern that is consistentwith the pattern of the sensed sense elements 44, where the pulses havea consistent width that is aligned with a portion of the sensed senseelements 44, a consistent width or spacing between pulses that isaligned with a width or spacing between the sensed sense elements 44,and a consistent amplitude, A, (e.g., where the consistent amplitude maybe due to the constant and consistent depth of the sense elements 44that are sensed).

Similar to as discussed above with respect to FIG. 11, the controller 12may monitor the signal 72 over time and based on the pattern of thesignal 72 over time (e.g., as depicted in FIGS. 12A, 12B, 12C, 13A, 13B,and/or other pattern of the signal 72), determine an axial position ofthe sense elements 44, the collar 48, and/or the rotor portion 22 b.Based on the axial position of the collar 48 (or other portions of thedry gas seal 22 on which the sense elements 44 are disposed) and/orpredetermined associations between an axial position of the collar 48and associated positions of the rotor portion 22 b relative to thestator portion 22 a, the controller 12 may be able to determine acurrent axial position of the rotor portion 22 b relative to the statorportion 22 a, determine relative movements of the rotor portion 22 b,and/or asses a status or condition of the dry gas seal 22. In oneexample, the controller 12 may compare changes in, trends in, and/orother suitable analyses of pulses or other features of the signal 72over time to determine and/or identify a status or condition of the drygas seal 22. Alternatively or additionally, the controller 12 maycompare values of the signal 72 (e.g., values related to pulses in orother features of the signal 72 including, but not limited to,amplitudes of the pulses, widths of the pulses, width of spaces betweenpulses, etc.) to predetermined values (e.g., threshold values, values ina look up table, etc.) or may enter the values of the signal 72 into analgorithm to determine an axial position or an amount of axial movementof the collar 48, the dry gas seal 22, the rotor portion 22 a, and/orthe stator portion 22 b. The threshold values, the look up tables,and/or the algorithm may be developed or determined off-line duringtesting of the dry gas seal 22 and/or developed, determined, and/orupdated in real-time while the dry gas seal 22 is on-line and inoperation.

FIG. 14 illustrates an example method 100 of operating a dry gas sealmonitoring system having a dry gas seal (e.g., the dry gas seal 22and/or other suitable dry gas seal) forming a seal between a housing(e.g., the housing 18 and/or other suitable housing) and a rotatableshaft (e.g., the rotatable shaft 20 and/or other suitable rotatableshaft). The method 100 may include determining 110 when one of aseparation of a first seal face from a second seal face of the dry gasseal and a contact of the first seal face with the second seal faceoccurs (e.g., determining an occurrence of an operational condition) anddetermining 120 a rotational speed indicative of a speed of therotatable shaft. Determining an occurrence of one of the separation ofthe first seal face from the second seal face and the contact of thefirst seal face with the second seal face may be based, at least inpart, on a signal of an acoustic emissions sensor (e.g., the acousticemissions sensor 19 and/or other suitable acoustic emissions sensor), asignal from a speed sensor (e.g., the speed sensor 17 and/or othersuitable speed sensor sensing a sense element (e.g., the sense element44 or other suitable sense element) rotating with the rotatable shaft),and/or on one or more other suitable signals or parameters. Determininga rotational speed indicative of a speed of the rotatable shaft may bedetermined based, at least in part, on a signal from the speed sensorand/or other suitable signals or parameters. The signal from the speedsensor may be obtained by sensing a plurality of sense elements rotatingwith the rotatable shaft.

The method 100 may further include associating 130 the rotational speedthat is determined when there is an occurrence of the operationalcondition with the respective occurrence of one of the separation of thefirst seal face from the second seal face and the contact of the firstseal face with the second seal face, and determining 140 an operationalcondition of the dry gas seal based, at least in part, on theassociation of the rotational speed with the occurrence of one of orboth of the separation of the first seal face from the second seal faceand the contact of the first seal face with the second seal face.Further, in instances when the dry gas seal includes multiple sealinterfaces, the operational condition of the dry gas seal may bedetermined based, at least in part, on an association of the rotationalspeed with the occurrence of one of or both of the separation of thefirst seal face from the second seal face and the contact of the firstseal face with the second seal face for one or more of the multiple sealinterfaces.

The determined operating condition of the dry gas seal may be anysuitable operating condition of the dry gas seal. For example, thedetermined operating condition may be an indication that the dry gasseal is healthy, unhealthy, needs real-time maintenance, will needmaintenance in N units of time, will need maintenance in N cycles ofuse, needs to be shut down, and/or other suitable conditions relating tothe operation of the dry gas seal. Such determining of the operatingcondition of the dry gas seal may facilitate planning for maintenanceand/or down time of a machine or system using the dry gas seal, whichwill mitigate unexpected shutdown of systems and/or machines.

In some cases, determining an operating condition of the dry gas sealmay include monitoring, over time, rotational speeds associated withoccurrences of one of or both of the separation of the first seal facefrom the second seal face and the contact of the first seal face withthe second seal face. To facilitate monitoring speeds over time, a firstbaseline speed for the separation of the first seal face from the secondseal face during run-up may be established and a second baseline speedfor the contact of the first seal face with the second seal face duringrun down may be established. Then, once the baseline values areestablished the first baseline speed may be compared with the rotationalspeeds associated with occurrences of the separation of the first sealface from the second seal face and the second baseline speed may becompared with the rotational speeds associated with occurrences of thecontact of the first seal face with the second seal face to determinethe operating condition of the dry gas seal.

Although baselines may be established and utilized, other methods ofmonitoring and/or determining operating conditions of the dry gas sealare contemplated. In some cases, monitoring and/or determining operatingconditions of the dry gas seal may include comparing speeds at currentoccurrences of an operational condition of one seal face relative toanother seal face to a predetermined threshold value, a rolling averageof speeds associated with the N previous occurrences of an operationalcondition of one seal face relative to another seal face, comparing adelta change in speed between a speed at a current occurrence of anoperational condition of one seal face relative to another seal face anda speed at one or more previous occurrences of an operational conditionof one seal face relative to another seal face to a threshold value,and/or compare the speeds at occurrences of an operational condition ofone seal face relative to another seal face to one or more othersuitable value.

As discussed above, occurrences of the separation of the first seal facefrom the second seal face and/or the contact of the first seal face withthe second seal face at seal interfaces (e.g., the first seal interface35, the second seal interface 37, and/or other suitable seal interfaces)of the dry gas seal occur at low speeds (e.g., speeds of less than onethousand (1,000) RPMs) relative to operating speeds of a system (e.g.,compressor or other suitable system) to which the dry gas seal may beapplied (e.g., speeds within a range from about ten thousand (10,000)RPMs to about forty thousand (40,000) RPMs or greater). With existingspeed sensors configured to sense speeds of the rotatable shaft atoperating speeds, it is not possible to obtain an accurate speed of therotatable shaft and/or a rotor portion (e.g., the rotor portion 22 b orother suitable rotor portion) of the dry gas seal at the low speeds atwhich seal faces of a seal interface initially separate from one another(e.g., lift off) or initially come into contact with one another (e.g.,touch down), which typically occur at speeds less than about onethousand (1,000) RPMs, and more typically at speeds less than about fivehundred (500) RPMs. As such, existing speed sensors used for sensingoperating speeds of rotatable shafts cannot be used to accuratelydetermine speeds that are to be associated with lift off or touch downoperational conditions of the seal faces in a manner that allows foradequate monitoring of operating conditions of dry gas seals. Theimproved dry gas seal monitoring systems and methods discussed herein,however, may facilitate accurately determining speeds to be associatedwith lift off or touch down operational conditions of the seal faces andthus, facilitate accurately determining an operating condition of thedry gas seal based on the associated speeds in a manner that allows foradequate monitoring of operating conditions of dry gas seals.

It should be understood that this disclosure is, in many respects, onlyillustrative. The various individual elements discussed above may bearranged or configured in any combination thereof without exceeding thescope of the disclosure. Changes may be made in details, particularly inmatters of shape, size, and arrangement of steps without exceeding thescope of the disclosure. The disclosure's scope is, of course, definedin the language in which the appended claims are expressed.

What is claimed is:
 1. A method of operating a dry gas seal monitoringsystem having a dry gas seal forming a seal between a housing and arotatable shaft, the method comprising: sensing a sense element rotatingwith the rotatable shaft; obtaining a signal based on the sensing of thesense element rotating with the rotatable shaft; determining an axialposition of a rotor portion relative to a stator portion based on thesignal obtained, the rotor portion and the stator portion form a sealinterface of the dry gas seal between the rotatable shaft with which therotor portion is configured to rotate and a stationary housing; sensingtwo or more sense elements rotating with the rotatable shaft, the two ormore sense elements include the sense element; and determining arotational speed indicative of a speed of the rotatable shaft at speedsbelow one thousand (1,000) RPMs based on sensing the two or more senseelements rotating with the rotatable shaft; determining when one of aseparation of a first seal face and a second seal face and a contact ofthe first seal face with the second seal face occurs; associating therotational speed with an occurrence of one of the separation of thefirst seal face from the second seal face and the contact of the firstseal face with the second seal face; and determining an operatingcondition of the dry gas seal based on the rotational speed associatedwith the occurrence of one of the separation of the first seal face fromthe second seal face and the contact of the first seal face with thesecond seal face.
 2. The method of claim 1, wherein determining theaxial position of the rotor portion relative to the stator portion isbased on an amplitude of the signal obtained.
 3. The method of claim 2,wherein determining the axial position of the rotor portion relative tothe stator portion comprises comparing the amplitude of the signalobtained to a threshold value.
 4. The method of claim 1, whereindetermining the axial position of the rotor portion relative to thestator portion is based on one or more of an amplitude of the one ormore pulses in the signal, a pulse width of the one or more pulses inthe signal, and a width between consecutive pulses in the signal.